A delay-locked loop is capable of generating multiple clock phase outputs from a clock signal input. It is desirable to have a delay-locked loop which has reduced circuit component matching requirements while generating multiple clock outputs equally spaced about 360 degrees.
Prior art inventions disclose delay locked loops that utilize chains of delay elements and relatively complex control schemes to generate a set of clock signals. The delay-locked loop of U.S. Patent Publication No. 2004-0223571 receives an input clock signal, then generates a single delay adjust signal by means of a phase detector, and control circuitry. The single delay adjust signal then controls the delay time of all of the delay elements in the chain. At a minimum, the control circuitry of this application includes a counter control circuit with digital memory, and a digital-to-analog converter. The set of generated clock signals is then further processed by additional circuitry that includes a phase interpolator, selection circuitry, and other feedback controls.
It would be desirable to provide a delay lock loop that improved on existing designs and is better suited for high speed data applications.